Metal-oxide chemical sensors are based on the concept that gaseous analytes interact with a metal oxide sensitive layer at elevated temperatures of the sensitive layer in the range of more than 100° Celsius, and specifically between 250° C. and 350° Celsius. As a result of a catalytic reaction, a conductivity of the sensitive layer may change which change can be measured. Hence, such chemical sensors are also denoted as high temperature chemoresistors for the reason that a chemical property of the analyte is converted into an electrical resistance at high temperatures of the sensitive layer.
A chemical sensor can be a gas sensor for detecting one or more substances in a gas, and specifically in the air surrounding a portable multi-purpose electronic device such a mobile phone or a tablet computer. Hence, in a sample application it may be of interest to identify, if such air may contain analytes the chemical sensor is tuned to detect. Specific applications may include the detection of toxic gases, the detection of ethanol, sulphide compounds or other components in a user's breath, or the detection of other substances.
It is also known to arrange such a chemical sensor inside a housing of a portable electronic device, such as a mobile phone, for example. An opening may be provided in the housing for exposing the chemical sensor to a fluid to be analyzed.
It is seen as particular problem to adapt a multitasking CPU of such a portable electronic device to the specific control requirements for a chemical sensor. It can be very difficult to provide instructions for a CPU to maintain control of the chemical sensor's operations while the same CPU is tasked to control core functions such as data and voice communication. The steps required to prepare a chemical sensor for a measurement as well as the actual measurement typically happen on a timescale of several seconds. The processing units in portable electronic devices, however, are often not suited to maintain control of a process for durations exceeding one second.
In the light of the above, it is therefore seen as an object of the invention to improve a chemical sensor and a method for operating a chemical sensor that particularly is suited for mounting into the housing of a portable multi-purpose electronic device.